Welding Preheat Temperature
Estimate the preheat temperature for welding, Tp = 350·√(CE − 0.25), as a function of the steel's carbon equivalent (CE). Preheating reduces the cooling rate, giving hydrogen time to escape and preventing the formation of brittle martensite and cold cracks in the heat-affected zone. Steels with a high CE require more preheating. Enter the steel's carbon equivalent.
Resultado
—
Temperatura de pré-aquecimento
Por que aquecer uma peça antes de soldá-la? Para domar o resfriamento. Quando o cordão quente esfria rápido demais sobre um metal frio e espesso, três vilões se juntam: forma-se martensita (microestrutura dura e frágil) na zona afetada pelo calor, o hidrogênio dissolvido não tem tempo de escapar e fica aprisionado, e surgem tensões de contração. O resultado é a trinca a frio (ou trinca induzida por hidrogênio), que pode aparecer horas ou dias após a soldagem. O pré-aquecimento desacelera o resfriamento, dando tempo para o hidrogênio difundir e evitando a martensita. A estimativa Tp = 350·√(CE − 0,25) liga a temperatura ao carbono equivalente do aço: quanto mais ligado o aço, mais quente o pré-aquecimento (de zero, para aços doces, a 200 °C ou mais em aços de alta liga e grande espessura). Informe o carbono equivalente do aço.
Related Tools
Carbon Equivalent (CEq)
Compute a steel's carbon equivalent by the (simplified) IIW formula, CEq = C + Mn/6 + Cr/5 + Ni/15, weighting the alloying elements' effect relative to carbon on the hardening and cracking tendency. It is the key weldability index: a CEq below 0.40 indicates easily weldable steel; above 0.45–0.50 it requires preheating and care to avoid cold cracking. Enter the carbon, manganese, chromium and nickel contents (%).
Martensite Start Temperature Ms (Andrews)
Computes the Ms temperature, the point at which austenite starts transforming into martensite during quenching, using the linear Andrews equation: Ms(°C) = 539 − 423·C − 30.4·Mn − 17.7·Ni − 12.1·Cr − 7.5·Mo, with every content in mass percent. Nearly every element dissolved in austenite lowers Ms — cobalt and aluminium are the exceptions and raise it —, but carbon dominates by far: each 0.1 % of carbon drops Ms by 42 °C, nearly 14 times the effect of the same manganese content. Knowing Ms sets the martempering bath temperature, tells whether retained austenite will survive at room temperature, and predicts how severe the quenching stresses will be, because a low Ms makes the martensite expansion happen late, with the part already cold and rigid, and that is where cracks appear. The correlation is fitted to low-alloy steels with carbon up to roughly 0.6 %, and the page rejects compositions above 0.8 % carbon, where the extrapolation loses its footing. Enter the carbon, manganese, nickel, chromium and molybdenum contents.
Weld Cooling Time t8/5
Computes how long the heat affected zone takes to cool from 800 °C to 500 °C, the t8/5 parameter of EN 1011-2, from the heat input, the preheat temperature and the joint shape factor. The formula multiplies the term (6700 − 5 × preheat temperature) by the heat input, by the difference between the reciprocals of (500 − T₀) and (800 − T₀), and by the shape factor tabulated in the standard, which is 1.0 for a bead deposited on a plate and drops to about 0.9 for a butt weld and 0.67 for a fillet weld on a T-joint. Austenite decomposes in that range, so t8/5 decides the microstructure of the joint: cooling too fast forms martensite and opens the door to cold cracking, cooling too slowly coarsens the grain and destroys impact toughness, and most structural steels call for something between 5 and 25 seconds. The three-dimensional heat flow equation was adopted, valid when the plate is thick relative to the weld bead; in thin plate the flow is two-dimensional and t8/5 grows with the square of the heat input rather than in proportion to it. Enter the heat input, the preheat temperature and the joint shape factor.
Electrode Consumption
Estimate the number of electrodes needed for a weld by dividing the total mass of metal to deposit by the mass deposited per electrode (rounding up). It is a practical planning and budgeting calculation in stick-electrode welding, avoiding over-buying or stopping the job for lack of consumables. Enter the total weld mass and the mass deposited per electrode.
Martensite Fraction (Koistinen-Marburger)
Computes the fraction of austenite already transformed into martensite when quenching stops at a given temperature, using the Koistinen-Marburger equation, f = 1 − e^(−0.011·(Ms − Tq)), where Ms is the martensite start temperature and Tq the temperature at which the part stopped cooling. The result is the percentage of martensite formed — whatever is missing from 100 % stays as retained austenite, which is soft, dimensionally unstable and able to transform later in service, distorting the part. Because the exponent is linear in the temperature difference, 63 °C below Ms already converts half the austenite, but 209 °C are needed to reach 90 % and the end of the transformation is asymptotic, never exact — which is precisely why precision parts get a cryogenic treatment after quenching. Enter the steel Ms temperature and the quench stop temperature.
Weld Deposition Rate
Compute a weld's deposition rate by dividing the mass of deposited metal by the arc-on time, giving kg/h. It is a central indicator of process productivity: processes like submerged arc and MIG/MAG have far higher rates than stick electrode. Combined with the operating factor (actual arc time), it estimates a joint's output. Enter the deposited mass and the arc time.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.